1. Field of the Invention
The present invention relates generally to air delivery systems in clean rooms and, more particularly, to an air handling system for use in clean rooms applications where large volumes of particulate free, temperature and humidity controlled airflow are required.
2. Description of the Related Art
Many enterprises, such as scientific laboratories, micro-electronic manufacturers, testing labs, hospitals, and the like, require relatively clean air from which substantially all dust particles, micro-organisms, and pathogens have been removed. Further, the advent of high technology developments in aerospace, electronics, optics, telecommunications, robotics, medicine, and genetic engineering, among others known and those not yet contemplated, give rise to an ever growing need for “clean space” in manufacturing and research and development. The cleanest class of room according to federal standards is the Class 1 clean room. By way of comparison, Class 10,000 indicates that there are 10,000 or less particles of a size 0.5 micron and larger in one cubic foot of air and Class 1 indicates that there are 100 or less particles of a size 0.5 micron and larger in one cubic foot of air. Further, the contamination level of clean air is generally proportional to the number of air changes per hour that is caused to move through the space. When the clean room industry was established in the early 1960's, uniform mass air flow of HEPA (High Efficiency Particulate Absolute) filtered air was informally called “laminar flow” because of the uniform velocity or non-turbulent (laminar) flow of air either vertically or horizontally across the work space. As is well established, a typical clean room includes walls, floor, and ceiling, an air supply feeding a duct or plenum, a fan, and a filtration system generally comprising a plurality of panels hung below the ceiling securing a series of HEPA filters for filtering the air flow.
More particularly, the contamination level of clean space is generally proportional to the number of filtered air changes per hour that is caused to move through the space, which may also be correlated with energy usage. The air exchange rate generally varies from a low of about 20 air changes per hour to a high of about 200 to 300 (or more) air changes per hour depending on the application. The higher the air exchange rate the cleaner the room, and the larger the quantity of in-line components required, each of which introduces its own sources of inefficiencies. The present invention is intended to directed address and reduce the prior art energy inefficiencies.
As noted above, clean room air delivery systems are generally designed to filter out dirt and dust particles of a very small size, correct the humidity and temperature of the air, and supply that air into the clean room in a generally laminar airflow pattern. The laminar airflow may be either vertically downward from the ceiling to the floor, horizontally from one side of the clean room space to the other, or horizontally across the clean room work surface, and then downward to the floor. The vertically downward airflow direction is the most common in the industry. The volume of air delivery to the clean room ranges from approximately 30 cubic feet per minute to 120 cubic feet (or more) per minute per square foot of clean room floor space. This volume compares to 1.0 to 1.5 cubic feet per minute per square foot of floor space in a typical office building. Such clean room air delivery systems are often used in critical clean rooms such as certain aerospace and semiconductor manufacturing clean rooms, but have numerous applications where a particulate-free, temperature and humidity controlled environment is required.
The rising cost of energy related to clean room operations has reached critical cost levels. An important aspect of increased costs is the seemingly never-ending increase in energy costs necessary to operate at desired filtration standards in a cost-effective manner. Increased filtration requirements generally require higher air flow rates in combination with efficient use of HEPA filters for cost efficient use of the resulting clean space. However, turbulent distribution of air requires a greater number of air changes to achieve a given level of efficiency, wasting energy with resulting increases in energy usage and costs. Further, the costs of operating certain clean room elements, such as cooling coils, also directly and negatively impacts operational costs. Specifically, it is known that the related art commonly provides for the installation of a cooling coil in tandem with each supply fan, and operation of each such cooling coil necessarily adds to the heat load to be cooled, as well as including substantial costs related to unit costs for cooling coils and related hardware associated with each supply fan/cooling coil combination. Further, in such combination, an output airflow from each supply fan/cooling coil combination is now measurably hotter than the input airflow due to the heat output related to each additional cooling coil, which in turn must be compensated for by upsizing the entire system, also further negatively effecting operating efficiencies. Upsizing requirements include a significantly increased fan size. By way of example, it is known that cooling coils are designed with a restriction in air velocity therethrough which generally cannot be designed in excess of 500 feet/minute, in turn requiring a significant increase in the size of the fan and the fan box to support an increased cooling air flow, thereby further introducing additional size, weight, cost, and installation considerations and impediments.
Accordingly, it is clear there is a need for an improved clean room system design that lowers energy costs, decreases construction time lines, easily adapts to changing manufacturing space requirements, and can be readily constructed within current guidelines. The clean room system based upon such a design should be easily incorporated with respect to areas of any size, clean room expansion, filter requirements, and the like, “dirty” air return locations, lighting locations and fire sprinkler layout. The system should afford the ability to utilize automatic material handling systems (AMHS) and other production equipment from the ceiling grid without having to penetrate or otherwise modify any air barriers. The system should also not negatively affect the time required to achieve the critical air balance requirements.
The foregoing and other objectives of the invention will become apparent in light of the drawings, specification and claims contained herein. It should be noted and understood that with respect to the embodiments of the present invention disclosed herein, the materials and apparatus disclosed and suggested may be modified or substituted to achieve the desired protected structures without departing from the scope and spirit of the disclosed and claimed invention.